This section provides background information related to the present disclosure, which is not necessarily prior art.
Incomplete combustion of the gasses and fuel mixture within the combustion chamber of an internal combustion engine can occur for a variety of reasons. Incomplete combustion can lead to inefficient operation of emission control equipment, such as catalytic converters, and increased emissions.
Secondary air injection systems (“SAI systems”) are one way to reduce the emission of the products of incomplete combustion. SAI systems inject external air into the exhaust, upstream of emissions equipment, such as the catalytic converter. The injected air reacts with the incompletely combusted exhaust and, in the case of a catalytic converter, this reaction heats the catalytic converter to allow more efficient operation.
It can be beneficial to know when an SAI system develops a leak or becomes blocked. One method of detecting such a condition is by measuring pressures in the SAI system. Generally, certain pressure profiles are expected in an SAI supply line to a given cylinder head when the SAI valve is open to that cylinder head. Other pressure profiles are expected when the SAI valve for that particular cylinder head is closed. An alert, such as a check engine light, can inform users when the pressure profiles are not as expected. However, pressure fluctuations from other cylinder heads can propagate through the SAI system and cause pressure measurements for a given cylinder head to vary outside the expected profile, thus erroneously indicating an SAI system failure. This can be especially true for V-engines, where the cylinders on opposite sides of the “V” are particularly close and the SAI valve is open to one while closed to the other. The configuration of many SAI systems can allow opposite cylinder heads to cause pressure fluctuations in each other, causing erroneous failure indications.